Controlled variable time radio proximity fuze

ABSTRACT

1. In a radio-controlled proximity fuze having a portion adapted to be rotated to set effective target time, a clock within said fuze adapted to be started when a projectile containing said fuze is fired, said rotatable portion being provided with at least two pairs of electrical contacts the first of which is adapted when short-circuited to close an electrical circuit to activate said fuze and the second of which is adapted when short-circuited to maintain said fuze unarmed, and means short-circuiting said second pair during a portion of the flight of the projectile and rotatably driven by said clock for sequentially short-circuiting said first pair and maintaining said electrical circuit closed and removing the short circuit across said second pair after predetermined intervals in flight which are functions of said affective target time.

United States Patent Kopec et al.

[ 51 Oct. 24, 1972 Jr.; Frederick H. Tenney, all of Rochester, N.Y.

[73] Assignee: The United States of America as represented by the Secretary of the Navy 22 Filed: Sept. 20, 1951 21 Appl.No.: 247,462

pages 888- Bonner The Radio Proximity Fuse, 893 of Electrical Engineering for Sept.

Published by Amer. Inst. of Elect. Engrs. 33 W. 39th St. N.Y. l8, N.Y.

I-Iinman, Jr. et a]. National Bureau of Standards Research Paper 1723, Vol. 37, July 1946, Radio Proximity Fuse Design Primary Examiner-Thomas I-I. Webb Attorney-G. L. Rubens and Claude Funkhouser EXEMPLARY CLAIM 1. In a radio-controlled proximity fuze having a portion adapted to be rotated to set effective target time, a clock within said fuze adapted to be started when a projectile containing said fuze is fired, said rotatable portion being provided with at least two pairs of electrical contacts the first of which is adapted when shoit-circuited to close an electrical circuit to activate said fuze and the second of which is adapted when short-circuited to maintain said fuze unarmed, and means short-circuiting said second pair during a portion of the flight of the projectile and rotatably driven by said clock for sequentially short-circuiting said first pair and maintaining said electrical circuit closed and removing the short circuit across said second pair after predetermined intervals in flight which are functions of said affective target time.

PATENTEDI BI 24 I 2 3 699 .892

SHEET 1 [1F 4 John C Kopec Henry 0. Schml'ft Jr. Frederick IZTbnn ey INVENTORS BY JMM ATTORNEYS PATENTED B I97? 3,699,892

Henry 0. SchmilfJn Frederick Ii-Tenney INVENTORS ATTORNEYS PATENTEDUET 24 I972 SHEET 4 [1F 4 0f TON/170R N Y E0 6 ME 5 M ANS M W T A R R m B H O l TRC A LII mi 3 OM 7 m M F I T B C 0 0 W Mm m 3 m M I :T r A 5 0 w? 6 9 u mm F E w s n w f" T0 OSCILLATOR AND *T" AMPLIFIER PLATE I77 CIRCUITS SOURCE OF Fl/fi/IVGSIGMLA John C. Kopec Henry 0. SchmiffJl:

FrederickliTenney INVENTORS BY L0 AT TORNEYS CONTROLLED VARIABLE TIME RADIO PROXIMITY FUZE This invention relates to radio fuzes for projectiles, and in particular to radio proximity fuzes which are energized and armed for only a predetermined interval, instead of during the entire flight of a projectile.

Conventional radio-controlled proximity fuzes which arm and become energized early in flight have serious limitations in use. Armed and energized radio fuzes are hazards to friendly aircraft flying beyond and at altitudes considerably greater than that of the target as well as to friendly troops, ships, and surface installations. in addition, such radio-controlled fuzes cannot be used in areas where low flying scout planes are operating because of the danger to such friendly aircraft. Fuzes which arm and become energized early in flight are susceptible both to interference from friendly radar and to enemy counter-measures during the remainder of the trajectory of the projectile.

It is an object of the invention to provide a radio proximity fuze which is fully armed and energized for only a predetermined interval instead of during the entire flight of a projectile.

It is also an object of the invention to provide a radiocontrolled proximity fuze in which the time in flight at which the fuze arms can be set into the fuze. The word arm is used hereinafter in the specification and in the appended claims to mean the removal of the final fuze safety device, e. g., the short circuit across the electrical detonator which is adapted to initiate by chain reaction through an intermediate charge the explosion of the filler of a projectile in which the fuze is mounted. It is intended that the words energized and activated connote that the conventional oscillating detector, amplifier and thyratron circuits within the radio fuze are electrically energized, i.e., that the radio circuits within the fuze are electrically energized. The radio circuits of a radio-controlled fuze are normally energized a short interval before the removal of the short circuit across the detonator to prevent premature detonations due to electrical transients, and in one connotation thereof the word arming can be considered to include the step of electrically energizing the radio circuits. However, in order more accurately to describe fuze operation, the energization of the radio circuits will hereinafter be considered to be entirely independent of the step of arming. The word bracket is herein intended to connote the active period during which the fuze is fully armed and energized. Self-destruction is intended to mean the firing of the electrical detonator due to internal functioning of the fuze in order to initiate the explosion of the powder train of the projectile. Another object of the invention is to provide a radio-controlled proximity fuze in which the time in flight at which the fuze becomes energized can be set into the fuze. A further object of the invention is to provide a radiocontrolled proximity fuze which is adapted to arm in flight a predetermined interval before the preset target time.

A still further object of the invention is to provide means in a radio-controlled proximity fuze to arm and energize the fuze a few seconds prior to the calculated time of arrival at the target, whereby the fuze is safe in flight over friendly troops and ships and through the area in which the bulk of friendly aircraft is operating.

During the unarmed and inactive portion of the trajectory the fuze is free from early bursts and entirely immune to external interference. Controllable arming for field artillery fuzes affords complete protection for friendly scouting'planes.

It is a further object of the invention to provide a radio-controlled proximity fuze in which the time in flight at which self-destruction occurs can be set into the fuze. Adjustable self-destruction time localizes the lethal area created at a predetermined altitude beyond the target and thereby eliminates the hazard to friendly aircraft flying beyond and at higher altitude than the target, to friendly troops and installations on approach to the ground, and to surface ships beyond the target.

Another object is to provide a radio-controlled fuze which is capable of multiple setting and resetting without loss in accuracy of the preset target time. A further object is to provide such a radio fuze which is capable of multiple settings by rotation of the nose portion in either the clockwise or the counterclockwise direction without impairing the accuracy of the final target time setting made before the projectile is fired.

It is still another object of the invention to provide a radio fuze in which the interval in flight at which arming occurs is a function of the target time set into the fuze. A further object of the invention is to provide a radio fuze in which the second limit of the bracket is a function of the preset target time. Still another object of the invention is to provide a radio fuze in which both limits of the bracket are functions of the preset target time. It is a still further object to provide in a radio fuze means for energizing the fuze after an interval in flight dependent upon the target time setting. Another object is to provide means for arming the fuze a predetermined interval after the fuze is energized. A still further object is to provide means to self-destroy the fuze at a predetermined interval after the preset target time.

It is also an object of the invention to provide means in a radio fuze to arm and energize the fuze a predetermined interval after a projectile is fired if no target time setting is made. A still further object is to provide means in a radio fuze to self-destroy the fuze after a predetermined interval in flight if no target time setting is made.

Another object of the invention is to provide means to maintain electrical connections between the nose portion, which is rotatable to set target time into the fuze, and the body of the fuze as they are rotated relative to each other.

In accordance with the invention the conventional antenna and the conventional oscillating detector, amplifier and thyratron circuits of the radio fuze are contained within a generally conical nose tip which completes the ogival contour of a projectile, and the conventional deferred action type battery is contained within a cylindrical portion extending rearwardly from the nose tip and adapted to fit within the generally tubular sleeve portion of the fuze. The conical nose tip and cylindrical portion are rotatable relative to the sleeve portion to allow target time settings to be made. A clock adapted to be started when the projectile is fired is mounted within the tubular sleeve portion. A plurality of electrical contacts insulated from each other are mounted on the cylindrical portion of the rotatable nose tip, and adjacent contacts are connected to opposite sides of electrical circuits within the nose tip. Shorting members rotatably driven by the clock are adapted to short-circuit between certain of said adjacent contacts and thus open and close electrical circuits when rotated by the clock. The phrase shorting member" is used hereinafter in the specification and in the appended claims to mean an electrically conducting member adapted to bridge across two electrical contacts and thus complete an electrical circuit therebetween and to remove the short circuit if moved so as to no longer bridge the contacts; shorting member is used whether the member, when moved, shortcircuits or unshorts the electrical contacts, i.e., whether it opens or closes an electrical circuit. Rotation of the nose tip relative to the sleeve portion to set target time into the fuze changes the separation between the contacts and the shorting members and thus the time required for the clock to bring the shorting members into short-circuiting (or unshorting) relation of said adjacent contacts.

The fuze of the invention is constructed in various ways, e.g., so that the interval in flight at which arming occurs, the interval at which the fuze becomes energized, or the interval at which self-destruction occurs can be set into the fuze, said arming, energization, or self-destruction being singularly or in combination made to occur at, at a predetermined interval before or after, or as some other function of, the preset time, or effective target time", which is used hereinafter in the specification and the appended claims to mean any one or combination of these intervals. Thus the phrase effective target time is meant to cover the time setting made on a field artillery fuze in which the fuze arms and energizes at a predetermined interval before the calculated time of arrival at the target and self-destroys only on impact, as well as the time setting on an antiaircraft fuze in which arming and energization are at predetermined intervals before the calculated time of arrival at the target and self-destruction occurs at a predetermined interval after this calculated and preset time. The phrase effective target time is also meant to cover the time setting on an antiaircraft fuze in which the intervals in flight at which arming, energization, and self-destruction occur are all functions of the preset time. It is often desirable that an antiaircraft fuze energize and arm, i.e., the first limit of the bracket occur, before the calculated time of arrival at the target (which time is set into the fuze) and that the fuze selfdestroy, i.e., the second limit of the bracket occur, after this calculated and preset time. The alternative embodiments herein described are both self-destroying at predetermined intervals after this preset time, or effective target time, and the phrases second limit of the bracket, and interval in flight at which selfdestruction occurs" are used interchangeably.

In the most preferred embodiment of the invention, the shorting members and arcuate electrical contacts are disposed on contiguous faces of a pair of juxtapositioned coaxial disks of insulation one of which engages said rotatable nose tip through said cylindrical portion and the other of which is rotatably driven by said clock. The contacts are concentrically arranged in radially separated positions on the face of one disk with pairs of radially aligned contacts connected to the opposite sides of electrical circuits within the rotatable nose.

Conductive shorting members on the contiguous face of the other disk are adapted to sequentially short-cir cuit (or unshort) said radially-aligned contacts as said disks are rotated relative to each other. The contacts and shorting members are positioned to energize and arm the fuze after intervals in flight which are functions of the preset target time. Means are provided to open electrical circuits to certain contacts and to close electrical circuits to other contacts in order to energize and arm the fuze a predetermined interval after the projectile is fired and to self-destroy the fuze after a predetermined interval in flight if no target time setting is made. A conventional electrically-actuated detonator is mounted within the tubular sleeve portion, and brushes urged resiliently outward from the cylindrical portion of the nose against spaced annular conducting rings disposed on the inner periphery of the tubular sleeve portion allow electrical connections from the detonator to the electrical circuits within the nose tip as it is rotated relative to the sleeve portion of the fuze.

In an alternative embodiment of the invention, an annular insulating ring engaging the cylindrical portion of the rotatable nose tip is provided with a plurality of electrical contacts on the inner circumference thereof with adjacent contacts adapted when short-circuited to switch electrical circuits within the nose tip. An insulating disk disposed within the annular insulating ring and rotatably driven by the clock is provided with shorting means comprising a plurality of circumferentiallyspaced, metalic radial pins extending through the outer periphery of the disk into metallic blocks. The radial pins are urged outward by both spring means and by centrifugal force against the inner circumference of the disk and against said contacts. When the nose portion is rotated to set target time into the fuze, the contacts are rotated relative to the shorting means to thus vary the interval after the projectile is fired and the clock is started before the disk is returned to a position where the radial pins can short circuit (or unshort) between adjacent contacts to accomplish the desired switching. If no time setting is made, the cooperating contacts and shorting means are adapted to sequentially accomplish electrical switching to energize, arm, and self-destroy the fuze at predetermined intervals after the clock is started; if a time setting is made the same switching sequence is accomplished, but the intervals are functions of the preset time.

Other objects of the invention will be apparent from the following description taken in connection with the accompanying drawing in which:

FIG. 1 is a partial sectional view through a radio fuze having a nose portion rotatable to set effective target time into the fuze; FIGS. 1a and lb are enlarged sections showing details thereof;

FIG. 2 is an exploded perspective view of the preferred embodiment of switching means within the fuze of FIG. 1 for energizing, arming, and self-destroying the fuze after intervals in flight which are functions of the target time setting, and in which view two of the elements (93 and 96) are rotated out of their normal perspective position to more clearly illustrate their construction;

FIG. 3 is a sectional view taken through the embodiment of FIG. 2;

FIG. 4 is a schematic view of the contacts inset on the rear face of the third plate of the switching means of FIG. 2;.

FIG. 5 is a view in perspective of the escapement mechanism of a centrifugally-operated clock;

FIG. 6 is a schematic circuit diagram illustrating the electrical switching accomplished by the embodiment of FIG. 2;

FIG. 7 is a view in perspective of an alternative embodiment of the switching means of FIG. 2;

FIG. 8 is a sectional view taken along line 8-8 of FIG. 7;

FIG. 9 is a sectional view taken along line 99 of FIG. 7; and

FIG. 10 is a schematic circuit diagram illustrating the switching accomplished by the embodiment of FIG. 7.

The radio fuze of the invention illustrated in FIG. 1 of the drawing is of conventional shape with a generally conical nose portion 11 contoured to complete the ogive of a projectile and a rearwardly extending tubular sleeve portion 12 adapted to fit within and engage the casing of a projectile. A hollowed, conical, plastic nose tip 13 at the front of the nose portion 11 contains a conventional interior antenna cap 15, oscillator coil 16, and oscillating-detector circuit (not shown) embedded in suitable plastic. The rear end of the plastic nose tip 13 is molded to a metallic nose base 17 having an outwardly extending flange 18. The front wall 20 of a frustrum-shaped, hollowed, metallic nose adapter 21 is adapted to support the plastic-embedded oscillatingdetector circuit (not shown) and the conical nose tip 13 with the rear face of the nose base 17 abutting against the wall 20. A forwardly extending annular lip 22 on the nose adapter 21 is crimped over the outwardly extending flange 18 of the nose base 17 to secure the nose adapter 21 securely to the nose tip 13 and form a hermetic seal therebetween.

A conventional amplifier circuit adapted to amplify the beat difference frequency between the signal radiated by the antenna 15 and the signal reflected from a target approached by the fuze and a conventional thyratron circuit adapted when triggered to initiate the explosion of the projectile are embedded in suitable plastic indicated generally at 23 within the hollowed nose adapter 21. A rearwardly extending tubular portion 24 of the nose adapter 21 is adapted to receive the front end of a generally cylindrical battery can 25 containing a conventional deferred action type battery (not shown). The inner periphery of the tubular portion 24 increases in diameter abruptly near the rear end thereof to form a thin-walled circumferential lip 29. An outwardly extending circumferential flange on the outer periphery of the battery can 25 near the front end thereof is adapted to fit snugly within the circumferential lip 29. In assembly, a gasket 31 of suitable compressible material, such as neoprene, is placed over the front cylindrical end of the can 25 and against the flange 30, and after the can 25 is inserted within the tubular portion 24, the circumferential lip 29 is spun over the flange 30 to join the battery can 25 and the nose adapter 21 solidly together and to form a hermetic seal between these parts. An opening 32 provided in the nose adapter 21 is adapted to snugly receive a pin 34 secured to the battery can 25 at the front end thereof to key these parts firmly together and prevent rotation therebetween. The nose tip 13, the nose adapter 21, and the battery can 25 are thus integral and turn as a unit within the sleeve portion 12 when a target time setting is made.

The generally tubular sleeve 12 has an outwardly extending portion 37 near the front end thereof contoured to continue the conical shape of the integral nose tip 13 and nose adapter 21. The inner periphery of the sleeve 12 near the front end thereof widens abruptly to receive the tubular portion 24 of the nose adapter 21 with the crimped-over portion of the lip 29 fitting within an annular groove 40 provided in and extending parallel to the axis of the sleeve portion 12. Opposing circumferential recesses 42 and 43 are provided respectively in the inner periphery of the sleeve 12 near the front end thereof and in the outer periphery of the tubular portion 24 of the nose adapter 21. A resilient split retaining ring 44 is compressed in diameter before insertion within the circumferential groove 42. After the nose portion 1 1 is inserted within the sleeve portion 12, screws protruding through the sleeve portion 12 near the front end thereof into the circumferential groove 42 are turned to force the retaining ring 44 partially into the circumferential groove 43, thereby preventing axial movement between the nose l1 portion and the sleeve portion 12.

The above described hollowed nose portion 11, nose adapter 21, and sleeve portion 12 and the means for rotatably joining the latter two elements, as well as the conventional oscillating detector, amplifier, and thyratron circuits therein contained, are well known in the art and do not constitute a part of the present invention. Similarly, the deferred action type battery and the means for mounting the electronic components of these circuits as well as the means for embedding the circuits in plastic are well known, and in order to simplify the detailed description and to facilitate the understanding of the invention, the details of the battery and of the oscillator, amplifier and thyratrons circuits are omitted from the drawing and are not described herein.

An auxiliary detonator 46 adapted to explode the booster charge of a projectile is contained within the tubular sleeve portion 12 near the rear end thereof. An electrically-actuated detonator 47, or electric primer, contained within the sleeve 12 is adapted when fired to explode the auxiliary detonator 46. A conventional mechanical time clock 49 adapted to start and run under the influence of centrifugal force assisted by torsional springs abuts against an inwardly extending radial shoulder 48 provided in the sleeve 12 in front of the auxiliary detonator 46. The escapement mechanism of a conventional centrifugally-driven torsional springassisted clock 49 is shown in perspective in FIG. 5. A main shaft 50 is driven by a pair of centrifugal gears 51 which are urged outward by both centrifugal force acting upon weights 52 mounted thereon and by torsional springs 53 abutting at one end against the weights 52 and coiled around centrifugal shafts 54 about which the gears 51 pivot. In the unoperated position before the projectile is fired, a pivoted escapement lever 55 is prevented from moving by a pivoted safety lever plate 56 which has a pin 57 protruding from its rear face. The pin 57 engages the escapement lever 55 and holds it in such a position that the teeth of the escapement gear 58 are engaged. Rotation of the escapement gear 58 turns the main shaft 50 through a reduction gear train. If the escapement gear 58 cannot turn, the main shaft 50 cannot rotate. The safety lever plate 56 is spin-detented by a retaining spring 59. When a projectile containing the clock mechanism is fired, the safety lever plate 56 rotates outward under the influence of centrifugal force against the forces of retaining spring 59, thereby supplying an initial impulse to and releasing the escapement lever 55. The escapement mechanism is thus unlocked by centrifugal force due to spin of the projectile. The initial movement sets up an oscillation of the escapement lever 55 which subsequently acts as a balance wheel to govern the speed of rotation of the shaft 50. The coiled springs 53, as well as centrifugal force acting on the weights 52, cause the centrifugal gears 51 to move outward and rotate the central shaft 50 and consequently the fourth plate 120 secured thereto. This rotation is slowed down by a series of reduction gears and pinions and its speed is determined by the regulated frequency of the escapement mechanism.

The invention is particularly concerned with the means for varying the intervals in flight at which arming, energization, or selfdestruction occurs. In the preferred embodiment of the invention the first limit of the bracket is a function of target time setting, i.e. the fuze is sequentially energized and armed at predetermined intervals before the calculated time of arrival at the target, i.e. before preset target time; the second limit of the bracket occurs a predetermined interval after the effective target time, i.e., self-destruction occurs a fixed interval in flight after the preset target time. A fuze having such characteristics is particularly suited for antiaircraft use aboard naval vessels. The preferred embodiment of means for arming, energizing, and self-destroying the fuze at intervals in flight dependent upon the preset target time is shown in exploded perspective view in FIG. 2, in cross section in FIG. 3, and in schematic circuit diagram in FIG. 6. A nonconducting circular first plate 60 is provided with a plurality of apertures 61 arranged in a circle concentric with the plate 60. An insulating circular second plate 62 coaxial with and of equal diameter to the first plate 60 is provided with a plurality of peripheral grooves 63 in the circumference thereof which register with the apertures 61 in the first plate. The registering apertures 61 and grooves 63 are adapted to receive cylindrical jacks 64 (See FIG. 1) extending rearwardly from the rear wall 65 of the battery can 25. The first and second plates 60 and 62 are secured to the rear wall 65 as hereinafter explained and rotate with the can 25, which in turn is integral with the nose adapter 21 and the conical nose tip 13.

An annular conducting ground ring 66 and an annular conducting condenser" ring 67 are inset in spaced relation to each other in the inner peripheral face of an annular insulating ring 68 which in turn is supported against the inner periphery of the sleeve 12 opposite the second plate 62 (See FIG. l). The conducting rings 66 and 67 are connected by insulated wires 70 and 71 respectively to opposite sides of the electric detonator 47 supported within the tubular sleeve 12.

The second plate 62 is provided with a first radial groove 73 in the front face thereof and a second radial groove 74 (See FIG. 3) in the rear face thereof with an angular displacement between the grooves 73 and 74. A metallic condenser brush 75 of generally parallelepiped shape is adapted to slide radially within the first groove 73; a metallic ground brush 76 of like shape is similarly adapted to slide within the second radial groove 74. A resilient spring 78, having a portion thereof contoured to fit snugly within a curved recess 79 in the front face of the second plate 62, protrudes into a longitudinal slot 80 in a radial side 81 of the brush 75. Radially inward movement of the brush 75 causes the spring 78 to abut against one end of the longitudinal slot 80 and bends the brush spring 78. When assembled within the sleeve portion 12, a radially outward extending triangular tip 83 on the brush 75 is urged against the annular condenser ring 67 by the bending forces in the spring 78 and by centrifugal force when the projectile is rotated. As illustrated schematically in FIG. 6, a wire secured to the radially inward face of the brush 75 is connected to a firing condenser 84 in the firing circuit of the fuze. When the nose portion 11 is rotated relative to the sleeve portion 12 to set effective target time into the fuze, the tip 83 of the outwardly urged brush 75 maintains electrical contact against the ring 67 and thus maintains electrical connection between one terminal of the detonator 47 and the firing circuit within the nose portion 1 1.

In a similar manner a spring 86 fitting snugly within a curved recess 87 in the second plate 62 is adapted to fit within a longitudinal slot 88 (See FIG. 3) in a radial side of the rush 76. Bending forces in the spring 86, and centrifugal force when the projectile is rotated, urge the triangular tip 90 on the radially outward face 91 of the brush 76 against the ground ring 66. As shown schematically in FIG. 6, a wire secured to the radially inward face of the contact 76 is connected to electrical ground in the firing circuit of the fuze.

An insulating third circular plate 93 of equal diameter to and coaxial with the plates 60 and 62 is provided with a plurality of concentric arcuate conducting contacts inset on the rear face thereof. The contacts are arranged in radially-separated pairs which are wired to opposite sides of electrical circuits within the nose portion 11 as illustrated schematically in FIG. 6 and hereinafter explained. Plate 93 is rotated out of its normal perspective position in FIG. 2 in order to better illustrate the arrangement of the electrical contacts. A recess 95 contoured to receive a generally U-shaped ring support 96 is provided in the rear face of third plate 93. In assembly, a plurality of screws 98 passing successively through apertures in the ring support 96, third plate 93, second plate 62, and first plate 60 engage threaded holes (not shown) in the rear wall 65 of the cylindrical battery can 25. The insulating plates 60, 62, and 93 are thus held integral and rotate with the nose portion 11 when efi'ective target time is set into the fuze.

Shorting means are provided as hereinafter described to sequentially short-circuit (or unshort") between radially aligned pairs of contacts and thus switch electrical circuits within the nose portion 11. The central angle subtended by the arcuate contacts and their relative positions determines the sequence and time intervals at which the desired electrical switching is accomplished. Electrical connections are made from the electrical contacts to radio circuits within the nose portion 1 1 by wires passing through the plates 93 and connecting to jacks 64 secured to the rear wall 65. To shorten the description and to facilitate the understanding of the invention, these wires are shown only schematically in the drawing and are described herein only in connection with FIG. 6.

An inner ring conducting contact 100 and an arcuate contact 101 of slightly larger radius and subtending a central angle of almost 360 are inset in coaxial and radially separated positions in the rear face of the third plate 93. An arcuate contact 102 coaxial with and of the same radius as the arcuate contact 101 and subtending only a relatively few degrees of arc is disposed midway of the open portion of the contact 101. The circumferential length between adjacent edges of contacts 101 and 102 covers a central angle 4) (See FIG. 4). A pair of arcuate and radially aligned and spaced contacts 103 and 104 coaxial with the contacts 100, 101, and 102 and also inset on the rear face of the third plate 93 subtend a central angle greater than and including the central angle 4). The contacts 103 and 104 thus overlap in a radial direction the adjacent edges of the contacts 101 and 102. A pair of arcuate and radially aligned and spaced contacts 105 and 106 respectively at the same radius as and disposed approximately diametrically opposite from contacts 103 and 104 subtend a relatively small central angle.

A circular insulating fourth plate 120 having its front face contiguous to the rear face of the third plate 93 engages and is rotatably driven by the shaft 50 of the clock 49. A resilient dish-shaped washer 121, such as a Belleville spring, inserted over the shaft 50 and compressed between the clock 49 and the fourth plate 120 resiliently urges the third and fourth plates 93 and 120 together. A pair of radially-aligned and radiallyseparated metallic shorting members 122 and 123 are provided on the front face of the fourth plate 120. Radially-aligned embossings 125 and 126 provided on the inner shorting member 122 are adapted to respectively abut against and electrically short circuit between the ring contact 100 and the contacts 101 and 102 as the third and fourth plates 93 and 120 are rotated relative to each other. Similarly, radiallyaligned embossings 127 and 128 on the outer shorting member 123 are adapted to respectively wipe across and short-circuit between the contacts 103 and 104 and to respectively wipe across and short-circuit between contacts 105 and 106, as the plates 93 and 120 are rotated relative to each other.

A deep, generally T-shaped recess 110 provided in the front face of the second plate 62 is contoured to receive a centrifugally-operated switch 130 having a metallic body 131 of rectangular cross sections. As hereinafter explained, when a projectile is fired the centrifugal switch 130 is driven radially outward within the recess 110 to accomplish electrical switching when no time setting is made on the fuze, but is prevented from outward movement if a time setting is made. Flat metallic contacts 112, 113, and 114 disposed within elongated slots 116, 117, and 118 respectively in the front face of the second plate 62 form part of the wall of the crosspiece section of the T-shaped recess 110.

Embossings on the centrifugal switch are urged against the contacts 112, 113, and 114 to complete electrical circuits as hereinafter explained.

A block of insulating material 132 fitting snugly within a groove 133 of U-shaped cross section in the radially-inward face of the body 131 of the centrifugal switch 130 is secured thereto by a pin 134. A pair of flat metallic plates 135 and 136 (See FIGS. 2 and 6) are secured in coplanar and spaced position against the radially inward face of the insulating block 132 by a pair of screws 137 and 138 respectively. The plates 135 and 136 are thus insulated from each other and extend beyond the ends of the block 132, and a radially-inward extending embossing 139 on the plate 135 abuts against the fiat face of the contact 112 in the normal unoperated position of the centrifugal switch 130. Radially-outward extending embossings 140 and 141 on the plates 135 and 136 are moved into engagement with the flat faces of contacts 113 and 114 respectively when the centrifugal switch 130 is operated radially outward under the influence of centrifugal force.

The centrifugal switch 130 operates when the projectile is fired if no target time is set into the fuze and is prevented from operating if a target time setting is made. A cylindrical setback pin 143 fits within registering circular openings 144, 145, 146, and 147 (See FIG. 3) provided respectively in the first plate 60, the body 131, the bottom wall 148 of the T-shaped recess 110, and the third plate 93.

A circumferential groove 150 is provided in the setback pin 143, and a resilient split setback spring 151 bent into a loop is inserted over the pin 143 at the groove 150 and grips the pin 143 snugly. The outer diameter of the spring 151 is larger than the diameter of the aperture 146 in the bottom wall 148 of the T- shaped recess 110. The setback pin 143 normally fits within the apertures 144, 145, 146, and 147 with the setback spring 151 against the bottom wall 148 of the recess 110. The centrifugal switch 130 is thus normally prevented from outward movement within the recess 110 by the setback pin 143 abutting against the edges of apertures 144, 146, and 147. One wall 152 of the circumferential groove 150 is conical, and under the force of setback when a projectile containing the fuze is fired, the setback pin 143 is driven rearward causing the conical face 152 to spread the setback spring 151 outwardly and thus free the setback pin 143.

An elongated aperture 155 in the fourth plate 120 of sufficient size to receive the setback pin 143 is in registry with the apertures 144, 145, 146 and 147 when the fuze is set on Safe, i.e., target time setting is made. in this position the setback pin 143 is driven rearwardly through the elongated aperture 155 into an opening (not shown) provided in the clock 49 under the force of setback when a projectile containing the fuze is fired. The centrifugal switch 130 is thus freed and moves radially outward within the recess 1 10 under the influence of centrifugal force and breaks engagement between contacts 112 and 135 and brings contacts 113 and 135 and contacts 114 and 136 into engagement.

The inner ring contact 100, the arcuate contact 104, and the arcuate contact 105 are connected to the flat metallic contacts 112, 114, and 113 respectively by wires (not shown) passing through apertures in plates 93 and 62. The wires leading to these contacts 113 and 1 14 lie in curved depressions 157 and 158 respectively in the front face of the plate 62. The electrically-commoned contacts 104 and 114 are connected to a jack 64 on the rear wall 65 leading to the anodes of the oscillating detector, amplifier, and thyratron circuits within the nose portion 11. A lead secured under the head of the screw 137 lays in a depression 159 in the front face of the second plate 62 and is connected to the condenser brush 75 and through a jack 64 to the firing condenser 84 in the nose portion 11. A lead secured under the head of the screw 138 is connected to a jack 64 leading to the positive terminal of the B section of the deferred action type battery and also passes through apertures in the plates 93 and 62 and is connected to the arcuate contact 103. The arcuate contact 101 is connected by a wire to the ground brush 76. The arcuate contact 106 is connected to the contact 102 by a wire laying in a depression in the front face of plate 93 and by another lead to a jack 64 leading through a safety switch 161 in the nose portion to the positive terminal of the anode voltage B section of the deferred action battery.

If a target time setting is made by rotation of the nose portion 11 relative to the sleeve portion 12, the setback pin 143 is rotated out of registry with the elongated aperture 155 in the fourth plate 120. In this condition when a projectile is fired, the setback pin 143 abuts against the plate 120 and is prevented from moving rearwardly under the force of setback. Thus the centrifugal switch 130 does not operate when a target time setting is made.

The operation of the preferred embodiment of the invention can best be understood by considering the schematic circuit diagram of FIG. 6. When no target time setting is made, the fuze energizes and arms at relatively short predetermined intervals after setback and self-destroys after a predetermined interval in flight. The intervals required to energize and arm the fuze are determined by the time required for the projectile to develop sufficient centrifugal force to operate the switch 130 and to activate the deferred action battery, and the RC time required to charge the firing condenser 84 through the resistance 167. With no target time setting, the setback pin 143 is in alignment with the elongated aperture 155 in the fourth plate 120 as hereinbefore explained. When a projectile containing the fuze is fired, the setback pin 143 is driven rearwardly by the force of setback causing the conical face 152 to spread the setback spring 151 and free the setback pin 143, which is driven rearwardly through the apertures 147 and 155 into the clock 49. Movement of the setback pin 143 frees the centrifugal switch 130 which flies radially outward in the recess 110 under centrifugal force to break electrical contact between contact 112 and 135 and to bring embossing 140 on contact 135 into engagement with contact 113 and to bring embossing 141 on contact 136 into engagement with contact 114. A glass ampule (not shown) containin g electrolyte within the deferred action type battery is shattered by the force of setback in conventional manner, and centrifugal force distributes the electrolyte into the cells to activate the battery.

At the Safe setting (i.e., no target time setting) the embossings 127 and 128 on the shorting member 123 maintain a short circuit across contacts 103 and 104.

When sufficient centrifugal force is attained after the projectile is fired to distribute electrolyte to the cells of the deferred action type battery, voltage is connected from the B section of the battery through shorted contacts 103 and 104 to the oscillating detector, amplifier and thyratron circuits to energize the fuze (See FIG. 6). Make contacts 114 and 136 of the operated centrifugal switch 130 complete a second path connecting anode potential from the B section of the deferred action type battery to the oscillating detector, amplifier, and thyratron circuits. Centrifugal force keeps the switch 130 closed and thus maintains the fuze energized after the clock 49 has rotated the embossings 127 and 128 of the shorting member 123 past the contacts 103 and 104. The oscillating detector, amplifier, and thyratron circuits of the fuze are thus energized a relatively short predetermined interval after setback when no target time setting is made, and after the fuze arms a firing signal of sufficient amplitude derived from the combination of radiated signal and signal reflected from a target will trigger the thyratron 166 and fire the detonator 47 in the conventional manner.

When a time setting is made, the embossings 125 and 126 on the shorting member 122 normally short-circuit between ring contact 100 and arcuate contact 101 to maintain an electrical short circuit across the detonator 47 and thus keep the fuze unarmed. This short circuit is completed through contacts 112 and 135 and may be traced from one side of the detonator 47, over wire 71 and through condenser ring 67 and brush 75, contacts 135 and 112, short-circuited contacts 101 and 100, brush 76 and ground ring 66 over wire to the other side of detonator 47. In the Safe position of the fuze with no time setting, the shorting member 122 does not maintain a short circuit across the contacts 100 and 101 to keep the fuze unarmed. The resistor 167 and firing condenser 84 in combination provide an RC time delay to prevent firing of the detonator 47 until the projectile is well away from the gun and from gun crew personnel. The thyratron 166 cannot conduct to fire the detonator 47 until the voltage on the condenser 84 has risen to a predetermined value. The thyratron 166 when triggered acts as a switch to discharge the firing condenser 84 through the detonator 47 to ground in order to detonate the fuze, and it is only after the firing condenser 84 becomes fully charged through the resistance 167 that sufficient energy is stored therein to fire the detonator 47. The grid of the thyratron 166 is normally biased several volts negative by the C- section of the deferred action battery to prevent its conduction in the absence of a firing signal. The firing signal from the amplifier (not shown) is impressed on the thyratron grid and when its peak value drives the thyratron grid sufficiently toward the positive region, the thyratron 166 ionizes and fires the detonator 47. The firing circuit for the detonator 47 is from the firing condenser 84 through the brush and the condenser ring 67 to the detonator 47, the ground ring 66 and brush 76 to electrical ground. Opening of contacts 112 and 135 when the centrifugal switch 130 operates prevents the establishment of a short circuit across the detonator 47 when the clock 49 has rotated the shorting member 122 sufficiently to short-circuit between ring contact and arcuate contact 101. When no time setting is made the fuze thus arms a short predetermined interval after setback, which interval is controlled by the RC time delay of condenser 84 and resistor 167 as well as the interval required to activate the deferred action type battery.

Operation of centrifugal switch 130 also prepares a circuit for self-destruction 'of the fuze after a predetermined interval in flight by bringing contacts 135 and 113 into engagement and thus completing an electrical circuit from one side of the detonator 47 to arcuate contact 105. Centrifugal force starts the clock 49 which rotates the fourth plate 120 in a clockwise direction when viewed from the nose of the fuze. Due to the separation of the contacts 1 12 and 135 by operation of the centrifugal switch 130, short circuiting by the segment 122 between contacts 100 and .101 does not maintain a short circuit across the detonator 47 as hereinbefore explained. When the fourth plate 120 is rotated sufficiently by the clock 49 to cause the conducting segment 123 to short-circuit between contacts 105 and 106, anode potential from the B section of the deferred action type battery is connected directly to the squib 47 to detonate the fuze. This firing circuit may be traced from the positive terminal of the anode potential B section of the deferred action battery through the normally closed safety switch 161 in the nose portion 11, the short-circuited contacts 106 and 105, contacts 113 and 135 of the operated centrifugal switch 130, brush 75 and condenser ring 67, detonator 47, ground ring 66 and brush 76 to electrical ground. The angular displacement between the embossings 125 and 126 on the conducting segment 122 and the radially aligned contacts 105 and 106 predetermines the time in flight at which the fuze of the preferred embodiment of the invention self-destroys if no target time setting is made, and at the Safe setting the embossings 125 and 126 are approximately in radial alignment with the aperture 147 in the third plate 93.

Time setting can be made by rotating the nose portion 11 either clockwise or counterclockwise until the index on the nose portion 11 is in alignment with the desired time setting marking on the sleeve 12; an angular displacement between the shorting members 122 and 123 and the contacts 101-106 on the nose portion corresponding to the desired setting is attained whether the nose is rotated clockwise or counterclockwise, and multiple setting and resetting of target time can be made without impairment of the accuracy of the final setting. The plate 120 is illustrated in the drawing and described as being rotated clockwise by the clock 49 when viewed from the nose. By reversal of the position of the contacts 101-106 on the face of the plate 93, it is possible to have the clock 49 rotate the plate 120 counterclockwise and still perform exactly the same sequence of switching.

If a target time setting is made, the preferred embodiment of the fuze of the invention is energized and becomes armed at predetermined intervals before the time set and self-destroys at a predetermined interval after the preset target time i.e., both limits of the bracket are functions of the effective target time setting. The inset contacts on the face of the third plate 93 are disposed to arm the fuze approximately one second after the fuze is energized.

Setting target time into the fuze by rotation of the nose portion 11 relative to the sleeve portion 12 angularly displaces the setback pin 143 from its normal position in registry with the elongated aperture 155. Upon setback the pin 143 is driven rearwardly against the fourth plate 120 and is thus prevented from moving into the clock 49. The centrifugal switch 130 is prevented from operating radially outward under the influence of centrifugal force by the setback pin 143 abutting against the edges of the apertures 144 and 147 in the first plate 60 and the third plate 93 respectively. Setting target time into the fuze also angularly displaces the inset contacts on the rear face of the third plate 93 relative to the shorting members 122 and 123. With effective target time set into the fuze, the embossings 125 and 126 on the segment 122 short-circuit between the ring contact and the contact 101 to maintain an electrical short circuit across the detonator 47. This short circuit is from one side of the detonator 47 through the condenser ring 67 and brush 75, contacts 135 and 112 of the centrifugal switch 130, the ring contact 100 which is short-circuited to the contact 101 by the segment 122, the brush 76 and the ground ring 66 to the opposite side of the detonator 47. The shorting member 123 performs no function at this instant. The circuit from the contact to the firing condenser 84 is open at the contacts 113 and 135 of the unoperated centrifugal switch 130, and thus if the member 123 short-circuits between radially-aligned contacts 105 and 106, no electrical circuit is completed.

Centrifugal force from the spinning of the projectile drives the clock 49 which rotates the fourth plate through the shaft 50 in a clockwise direction when viewed from the nose of the fuze. The shorting member 122 maintains a short circuit across contacts 100 and to keep the fuze unarmed until a predetermined interval prior to the preset target time. The circuit to energize the fuze by connecting anode potential from the B section of the deferred action type battery to the oscillating detector, amplifier and thyratron circuits is open until the clock 49 rotates the fourth plate 120 to cause the embossings 127 and 128 on the shorting member 123 to short-circuit between radially-aligned contacts 103 and 104. This circuit may be traced from the positive terminal of the B section of the deferred action type battery through the short-circuited contacts 103 and 104 to the anodes of the oscillating detector, amplifier and thyratron circuits within the nose portion 11 of the fuze. The fuze arms when the fourth plate 120 is rotated until the embossing 126 comes off the contact 101 to remove the short circuit across the detonator 47. The radial angle 0 (See FIG. 4) subtended by the radially aligned contacts 103 and 104 is greater than and includes the angle q) subtended by circumferential separation between adjacent edges of contacts 101 and 102. The embossings 127 and 128 thus short-circuit between contacts 103 and 104 to energize the fuze a predetermined interval before the embossing 126 comes off the contact 101 to arm the fuze. This interval is predetermined by the radial angle X (See FIG. 4) that the radially-aligned contacts 103 and 104 overlap the contact 101 and the speed of rotation of the fourth plate 120, and in the preferred embodiment of the invention this interval is approximately 1 second. Energization and arming of the fuze are thus both functions of the preset target time. The fuze is thus safe in flight over friendly troops and ships and immune to radar interference and jamming during the unarmed and unenergized portion of the trajectory.

The clock 49 continues to rotate the fourth plate 120. The contacts 103 and 104 radially overlap the contact 102 to keep the fuze energized until the electric primer 47 is detonated. During the bracket the radio circuits within the nose portion 11 are energized and a continuous radio signal is radiated. A firing signal of sufficient amplitude furnished by the combination of the wave reflected from the target with the voltage of the oscillating detector will trigger the thyratron 166 to initiate the explosion of the projectile in the conventional manner. When the fourth plate 120 is rotated sufiiciently for the embossings 125 and 126 on the conducting segment 122 to electrically short-circuit between the ring 100 and the contact 102, a circuit is completed to connect anode potential through the detonator 47 to self-destroy the fuze. This circuit may be traced from the positive terminal of the anode B section of the deferred action type battery, the normallyclosed switch 161 within the nose portion 11, short-circuited contacts 102 and 100, contacts 112 and 135 of the unoperated centrifugal switch 130, brush 75 and condenser ring 67, the detonator 47, ground ring 66 and brush 76 to electrical ground. The bracket, i.e. the interval that the fuze is fully armed and energized, is determined by the angle 1) (See FIG. 4) subtended by the circumferential separation between the adjacent edges of contact 101 and 102. An antiaircraft fuze should be energized and armed prior to the time of arrival at the target and self-destroy after this target time, i.e., the first limit of the bracket is pre-target time and the second limit is post-target time. In the preferred embodiment of the invention effective target time markings in seconds are placed on the sleeve 12 so that when an index on the nose portion 11 is rotated to a desired time setting marking, an interval in accordance with the selected marking is required to rotate the embossings 127 and 128 on the shorting member 123 to a position approximately midway of the angle qb. Connecting anode potential through the detonator 47 selfdestroys the fuze a predetermined interval after the preset target time. Thus the predetermined intervals in flight at which the fuze activates, arms, and selfdestroys are all functions of the preset target time.

It is apparent that the length of the bracket may be changed as desired by varying the angle (1), i.e., by varying the circumferential separation between adjacent edges of contacts 101 and 102. In another modification of the invention the second limit of the bracket is at the effective target time. The intervals in flight at which the fuze activates, arms, and self-destroys can be readily varied by changing the separation between and radial angles subtended by the inset arcuate contacts on the rear face of the third plate 93, and the appended claims are intended to cover all such modifications.

An alternative embodiment of electrical switching means for energizing and arming a radio fuze after intervals in flight which are functions of the target time setting and for self-destroying the fuze a predetermined interval after the time set is illustrated in FIGS. 7 to 10. This modification of the switching means of the invention is intended for use in fuzes of antiaircraft projectiles having time settings over a range of from 5 to lOO seconds. An annulus 170 of a suitable insulating material, such as polymethylmethacrylate, is secured to the rear end 65 of the battery can 25 and is thus rotatable with the nose portion 11. A first pair of metallic contacts 171 and 172 inset in the inner periphery of the annulus are held in circumferentially separated positions by screws 174 (See FIG. 8) which pass through the annulus 170 from the rear end thereof. A second pair of metallic contacts 176 and 177 which individually subtend larger radial angles than the individual contacts 171 and 172 are inset and circumferentially separated along the inner periphery of the annulus 170 and similarly fastened to the annulus 170 by screws 174. Wires soldered to the contacts 171, 172, 176 and 177 pass through radial holes 180 in the annulus 170 and are connected to electrical circuits within the nose portion of the fuze as hereinafter described.

Secured to the shaft 50 of the clock 49 is a circular disk 181 of suitable insulating material such as polymethyl-methacrylate. The disk 181 is of slightly smaller diameter than the inner circumference of, and is rotatable within, the annulus 170. The shorting means of this embodiment of the invention includes a pair of metallic rectangular shorting blocks 183 and 184 inset in the front face and near the outer periphery of the disk 181 and secured in position by screws 185 passing through the disk 181 from the rear face thereof (See FIG. 9). A pair of circumferentially spaced radial holes 187 extend from the outer periphery of the disk 181 into the metallic shorting block 184, and two circumferentially spaced pairs of radial holes 187 similarly extend into the metallic shorting block 183. A pair of identical metallic radial pins 188 and 189 fit within the two radial holes 187 extending into the block 184; similarly identical metallic radial pins 190, 191, 192 and 193 fit within the two pairs of radial holes 187 extending into the block 183. Approximately midway of the length of these identical cylindrical pins 188 to 193 the diameter decreases abruptly to form a shoulder 194. The smaller diameter radially inward end of these pins 188 to 193 fits within helical springs 195 inserted within the radial holes 187 with the springs 195 abutting against the shoulder 194. The radial pins 188 to 193 are thus resiliently urged outward by the springs 191 against the inner circumference of the annulus 170, and an electrical short circuit is completed across any of the adjacent contacts 171, 172, 176, and 177 if the radial pins 188 and 189 or the pairs of pins 190, 191 and 192, 193 bridge across adjacent contacts. The shorting means of this embodiment of the invention thus includes the radial pins 188 to 193 and the shorting metallic blocks 183 and 184.

The radial angle A (See FIG. 10) subtended by the radial pins 188 and 189 is equal to the angle subtended by the circumferential length of the individual contacts 176 and 177, and in the Safe position with no target time setting the pins 188 and 189 are opposite the ends of the contact 176. As shown schematically in FIG. 10, the contact 176 is connected to the positive terminal of the anode voltage B section of the deferred action type battery of the fuze. The contact 177 is connected to the anode of the thyratron 166 through the resistor 167, and the firing capacitor 84 is connected between the anode of the thyratron 166 and the contact 171. One terminal of the detonator 47 is also connected to the contact 171, and the opposite terminal thereof is con- 17 nected to both contact 172 and to electrical ground. The electrical connections to the detonator 47 are through the condenser ring 67 and brush 75 and ground ring 66 and brush 76, but in order to facilitate the understanding of the operation of this embodiment of the fuze, these parts have been omitted from the circuit diagram of FIG. 10.

The radial angle B subtended by the circumferential length between the adjacent edges of the contacts 171 and 172 is slightly smaller than the angle C subtended by the middle two radial pins 191 and 192 extending into the metallic block 183. In the Safe setting, i.e., with no target time setting, the pair of radial pins 190 and 191 abut against the contact 171 and the second pair of radial pins 192 and 193 abut against the contact 172 to maintain an electrical short circuit across the detonator 47.

When the nose portion 11 is rotated to set time into the fuze, the contacts 171, 172, 176 and 177 are rotated clockwise relative to the shorting blocks 183 and 184 when viewed from the front of the fuze. The radial angle D subtended by the circumferential length between adjacent edges of contacts 171 and 176 is greater than the radial angle A subtended by the radial pins 188 and 189, and it is thus impossible for the radial pins 188 and 189 extending into the shorting block 184 to short-circuit between the adjacent contacts 171 and 176 and connect anode voltage from the B section of the battery to the ungrounded side of the detonator. When a projectile containing the fuze is fired, the centrifugally driven clock 49 starts as hereinbefore explained and rotates the disk 181 clockwise when viewed from the front of the fuze. After rotation of the disk 181 by the clock 49 through an angle dependent upon the time setting, the radial pins 188 and 189 complete a short circuit across contacts 171 and 172 and thus across the detonator 47, but no electrical switching is accomplished thereby.

Continued clockwise rotation of the disk 181 through its original Safe setting with the pair of radial pins 190 and 191 abutting against contact 171 and the pair of radial pins 192 and 193 abutting against the contact 172 again completes a short circuit across the detonator 47. At this instant the radial pins 188 and 189 abut against opposite ends of the contact 176. The circumferential separation between contacts 176 and 177 is only approximately one half the circumferential separation between the radial pins 190 and 191 and between radial pins 192 and 193, and thus upon continued rotation of the disk 181 the radial pins 188 and 189 short-circuit between contacts 176 and 177 to connect anode potential to the thyratron, oscillating detector, and amplifier circuits to energize the fuze before the trailing radial pins 191 and 193 are rotated past the contacts 171 and 172 respectively to remove the short circuit across the detonator 47 and thus arm the fuze It will thus be noted that the intervals in flight before the fuze is energized and arms, i.e., the first limit of the bracket, are functions of the target time setting. The radial pins 188 and 189 continue to short circuit between contacts 176 and 177 and thus maintain the fuze energized during continued rotation of the disk 18]. A firing signal of sufficient amplitude furnished by the combination of the wave reflected from the target with the voltage of the oscillating detector will trigger the thyratron 166 in the conventional manner to initiate the explosion of the projectile.

The angle E subtended by the circumferential separation between the outer radial pins 190 and 193 of the pairs of pins extending into the shorting block 183 is greater than the angle D subtended by the circumferential separation between the contacts 171 and 176, and after a desired bracket, i.e., period during which the fuze is fully energized and armed, outer radial pins 190 and 193 short-circuit between contacts 171 and 176 to connect anode B+ potential directly to the electrical squib 47 to explode the detonator 47 a predetermined interval after the calculated time of arrival at the target. The second limit of the bracket is thus post-target time.

The minimum time setting of the fuze of this embodiment of the invention is 5 seconds and a maximum time setting of seconds is provided. Such a range of target time setting is desirable in a fuze for field artillery antiaircraft fire. Such controllable arming affords complete protection for friendly scouting planes. At the Safe setting, i.e., when the nose portion 1 1 has not been rotated to set target time, the squib 47 is not detonated in flight until the clock 49 has rotated the disk 181 through a fixed radial angle, i.e., until radial pins and 193 short-circuit contacts 171 and 176 to connect B+ anode potential directly to the detonator 47. In this modification of the invention a time interval of five seconds elapses during the rotation of the disk 181 through this fixed radial angle before the fuze selfdestroys. With no time setting the predetermined interval after the clock 49 starts before the fuze activates is dependent upon the circumferential separation between contacts 176 and 177. With no time setting the fuze does not arm until the clock 49 rotates the disk 181 sufficiently to remove the trailing radial pins 191 and 193 off the contacts 171 and 172 respectively.

It is apparent that by varying the arcuate length of and relative separation between contacts, the intervals in flight at which the embodiment of the invention shown in FIGS. 7 to 10 is energized, arms, and selfdestroys can be made any desired function of, or independent of, the preset target time, and the appended claims are intended to cover all such modifications. For example, by circumferentially separating the contacts 171 and 176 a greater distance than radial pins 190 and 193 a fuze may be provided which arms and activates after intervals in flight which are functions of the preset target time but self-destruction will be independent of the time setting and may be made to depend upon impact, approach to the earth, or declaration to a predetermined minimum rotational velocity.

Having thus described several embodiments of our invention, we wish to point out that it is not confined to the specific structures shown but is of the scope of the appended claims. What we claim and wish to protect by Letters Patent of the United States is:

We claim:

1. In a radio-controlled proximity fuze having a portion adapted to be rotated to set effective target time, a clock within said fuze adapted to be started when a projectile containing said fuze is fired, said rotatable portion being provided with at least two pairs of electrical contacts the first of which is adapted when short-circuited to close an electrical circuit to activate said fuze and the second of which is adapted when short-circuited to maintain said fuze unarmed, and means shortcircuitin g said second pair during a portion of the flight of the projectile and rotatably driven by said clock for sequentially short-circuiting said first pair and maintaining said electrical circuit closed and removing the short circuit across said second pair after predetermined intervals in flight which are functions of said effective target time.

2. In a radio-controlled proximity fuze having a portion adapted to be rotated to set effective target time, switching means comprising a clock within said fuze adapted to be started when a projectile containing said fuze is fired, said rotatable portion being provided with three pairs of electrical contacts insulated from each other, the first of which is adapted when short-circuited to complete an electrical circuit to activate said fuze, the second of which is adapted when short-circuited to complete an electrical circuit to maintain said fuze unarmed, and the third of which is adapted when shortcircuited to complete an electrical circuit to selfdestroy said fuze, and means short-circuiting said second pair during a portion of the flight of the projectile and rotatably driven by said clock for sequentially short-circuiting said first pair, removing the short circuit from across said second pair, and short-circuiting said third pair at predetermined intervals after said prjectile is fired which intervals are functions of said effective target time setting.

3. Switching means for a radio-controlled proximity fuze in accordance with claim 2 and including a centrifugally-operated switch adapted when operated to close an electrical circuit to activate said fuze and to prepare an electrical circuit to self-destroy said fuze, a fourth pair of contacts on said rotatable portion adapted when short-circuited to complete said circuit to self-destroy said fuze, and means to prevent said centrifugal switch from operating if a time setting is made, and in which said short-circuiting means is adapted to short-circuit between said fourth pair of contacts a predetermined interval after said projectile is fired if no time setting is made.

4. Switching means for a radio-controlled proximity fuze in accordance with claim 2 and in which said shorting means is adapted to sequentially short-circuit across said first pair, remove the short circuit from across said second pair and to short-circuit said third pair at predetermined intervals after said projectile is fired if no time setting is made.

5. In a radio-controlled proximity fuze, a generally tubular body portion having an outwardly extending flange near the front end thereof contoured to form part of the ogive of a projectile, a generally conical nose portion contoured to complete said ogive and having a rearwardly extending cylindrical portion fitting and rotatable within said body portion to set efi'ective target time, means for preventing relative axial movement between said nose and said body portions, said nose portion containing a battery and amplifier and oscillating-detector circuits, an electrical detonator within said body portion, a clock also within said body portion adapted to be started when a projectile containing said fuze is tired, a pair of conducting rings within said body portion insulated from each other and spaced along the axis of said body portion with the rings connected to opposite sides of said detonator, a pair of brushes on said cylindrical portion each of which is resiliently urged against one of said conducting rings and connected to an electrical circuit within said nose portion, said cylindrical portion also being provided with at least one pair of electrical contacts insulated from each other and adapted to switch an electrical circuit within said nose portion when short-circuited together, and means rotatably driven by said clock and adapted to short-circuit said contacts.

6. In a fuze in accordance with claim 5 in which said rotatably-driven means short-circuits a pair of electrical contacts during a portion of the interval in flight and is adapted to remove this short circuit when rotated.

7. In a radio-controlled proximity fuze having an oscillating detector adapted to oscillate at radio frequency and to detect the difference beat frequency between the signal radiated by said fuze and a signal reflected from a target approached by said fuze, an amplifier for amplifying said detected signal, an electrically-actuated detonator adapted to initiate the explosion of said fuze, a grid-controlled gas-filled discharge tube adapted to actuate said detonator when triggered by the output of said amplifier, a battery, and a portion adapted to be rotated to set an effective target time, an energizing interval, an arming interval, and a selfdestruction interval; switching apparatus comprising means for normally maintaining a short circuit across said detonator, means for completing an electrical circuit during said self-destruction interval to connect said battery to said detonator in order to self-destroy said fuze after an interval in flight which is a function of said effective target time providing said fuze has not detonated from a signal reflected from a target, means for removing the short circuit across said detonator during said arming interval and a predetermined interval before said fuze self-destroys, and means for completing an electrical circuit during said energizing interval to connect said battery to said amplifier and said detector and said discharge tube a predetermined interval before the removal of said short circuit.

8. In a radio-controlled proximity fuse in accordance with claim 7 in which said switching apparatus includes a separate switching means operable when no time setting is made for completing an electrical circuit during said energizing interval to connect said battery to said amplifier and said detector and said discharge tube in order to activate said fuze a first predetermined interval after said projectile is fired, for removing said short circuit from across said detonator during said arming interval to arm said fuze a second predetermined interval after said projectile is fired, and for completing an electrical circuit during said selfdestruction interval to connect said battery to said detonator a third predetermined interval after said projectile is fired.

9. In a radio-controlled proximity fuze having an oscillating detector adapted to oscillate at radio frequency and to detect the difference beat frequency between the signal radiated by said fuze and a signal reflected from a target approached by said fuze, an amplifier for amplifying said detected signal, an electri- Cally-actuated detonator adapted to initiate the explosion of said fuze, a grid-controlled gas-filled discharge tube adapted to actuate said detonator when triggered from the output of said amplifier, a battery, and a portion adapted to be rotated to set effective target time; switching apparatus comprising a clock adapted to be started when a projectile containing said fuze is fired, a pair of juxtapositioned coaxial disks of insulation one of which engages said rotatable portion and the other of which is rotatably driven by said clock, a pair of spaced electrical contacts on the face of one disk one of which contacts is electrically connected to said battery, a centrifugally-operated switch having a set of normally open contacts adapted when closed to complete an electrical circuit to connect said battery to said amplifier and to said detector and to said discharge tube in order to activate said fuze and a set of breakmake contacts adapted when said switch is operated to open a circuit normally maintaining a short circuit across said detonator to arm said fuze and to electrically connect said detonator to the other of said spaced contacts, means to prevent said centrifugal switch from operating if a time setting is made, and a shorting member on the contiguous face of the other disk adapted to short-circuit between said spaced contacts a predetermined interval after said projectile is fired providing no time setting is made.

10. Switching apparatus in accordance with claim 9 in which said centrifugal switch is disposed in said rotatable portion and said means to prevent said centrifugal switch from operating includes a pin in the path of movement of said switch and removable therefrom by the force of setback from the firing of said projectile to release said switch, said pin projecting through an aperture in the disk engaging said rotatable portion, said disk driven by said clock having an opening therein in alignment with said pin through which said pin may pass to release said switch if no time setting is made, whereby when a time setting is made said pin is rotated out of alignment with said opening and operation of said centrifugal switch is prevented.

11. In a radio-controlled proximity fuze having an oscillating detector adapted to oscillate at radio frequency and to detect the difference beat frequency between the signal radiated by said fuze and a signal reflected from a target approached by said fuze, an amplifier for amplifying the output of said detector, an electrically-actuated detonator adapted to initiate the explosion of said fuze and having one side thereof connected to electrical ground, a grid-controlled gas-filled discharge tube adapted to actuate said detonator when triggered by a signal of sufficient amplitude and duration from said amplifier, a battery, and a portion adapted to be rotated to set effective target time; switching apparatus comprising a clock within said fuze adapted to start when a projectile containing said fuze is fired, a pair of juxtapositioned coaxial disks of insulation the first of which engages said rotatable portion and the second of which is rotatably driven by said clock, said first disk having a plurality of concentric arcuate electrical contacts on the face thereof including an inner ring contact normally electrically connected to the ungrounded side of said detonator, an arcuate second contact spaced radially from said inner contact and connected to electrical ground, an arcuate third contact having the same radius as said second contact and electrically connected to said battery and being disposed centrally of the open portion of said second contact, the circumferential separation between the second and third contacts subtending a central angle 4:, and a pair of arcuate radially-spaced outer contacts of greater radius than said second and third contacts and subtending a central angle including and greater than the angle #2, one of said outer pair being electrically connected to said battery and the other of said pair being electrically connected to the anode circuits of said detector and said amplifier and said discharge tube, said second disk having a pair of radially aligned shorting members on the contiguous face thereof the first of which is adapted to short-circuit between said ring and said second contacts when a time setting is made and to remove this short circuit after an interval in flight which is a function of said effective time setting and the second of which is adapted to short circuit between said pair of outer contacts a predetermined interval before said first shorting member removes the short across said ring and said second contacts as said second disk is rotated by said clock, said first shorting member being also adapted to short-circuit between said ring and third contacts after rotation through said angle 1).

12. In a radio-controlled proximity fuze having an oscillating detector adapted to oscillate at radio frequency and to detect the difference frequency between the radiated signal and a signal reflected from a target approached by said fuze, an amplifier for amplifying the output of said detector, an electrically-actuated detonator adapted to initiate the explosion of said fuze and having one side thereof Connected to electrical ground, a grid controlled gas-filled discharge tube adapted to actuate said detonator when triggered by a signal of sufficient amplitude and duration from said amplifier, a battery, and a portion adapted to be rotated to set effective target time; switching apparatus comprising a clock within said fuze adapted to start when a projectile containing said fuze is fired, a first pair of electrical contacts on said rotatable portion one of which is connected to electrical ground and the other of which is electrically connected to the ungrounded side of said detonator, a second pair of electrical contacts on said rotatable portion one of which is electrically connected to said battery and the other of which is connected to the plate circuits of said amplifier and said detector and said discharge tube, a contact member on said rotatable portion also electrically connected to said battery, means rotatably driven by said clock for short-circuiting said first pair of contacts when an effective target time setting is made, and adapted to remove the short circuit a first predetermined interval after said clock starts which interval is a function of said effective target time setting, means rotatably driven by said clock for short-circuiting said second pair of contacts a second predetermined interval after said clock starts, said second interval being shorter than said first interval and also being a function of said time setting, and means rotatably driven by said clock for short-circuiting the contact of said first pair which is connected to said detonator and said contact member a third predetermined interval after said clock starts which third interval is also a function of said effective target time setting and greater than said first intervalv 13. In a radio-controlled proximity fuze having a portion adapted to be rotated to set effective target time, an electrically-actuated detonator having one side thereof grounded and adapted to initiate the explosion of said fuze, an oscillating detector within said rotatable portion adapted to oscillate at radio frequency and to detect the beat frequency between the signal radiated by said fuze and a signal reflected from a target approached by said fuze, an amplifier within said rotatable portion for amplifying said detected signal, a grid-controlled gas-filled discharge tube within said rotatable portion adapted to actuate said detonator when triggered by the output of said amplifier, and a battery within said rotatable portion; switching means comprising a clock within said fuze adapted to be started when a projectile containing said fuze is fired, an annular insulating ring engaging said rotatable portion and provided with a first pair of spaced electrical contacts on the inner circumference thereof with each contact connected to an opposite side of said detonator and a second pair of spaced electrical contacts on the inner circumference thereof one of which is connected to said battery and the other of which is connected to the anodes of said detector and said discharge tube and said amplifier, an insulating disk within said annular ring rotatably driven by said clock and provided with first shorting means adapted to short-circuit said second pair of contacts a first predetermined interval after said clock starts which interval is a function of said effective target time, and second shorting means adapted to short-circuit said first pair of contacts during the shorting of said second pair and to remove the short circuit across said first pair a second predetermined interval after said clock starts which second interval is a function of said effective target time and longer than said first interval, said second shorting means also being adapted to short-circuit said contact of said first pair that is connected to the ungrounded side of said detonator and the contact of said second pair that is connected to said battery a third predetermined interval after said clock starts which interval is a function of said effective target time and greater than said second interval.

14. Switching means in a radio-controlled proximity fuze in accordance with claim 13 and in which, when no effective target time setting is made, said first shorting means is adapted to short-circuit said second pair of contacts a first predetermined interval after said clock starts and said second shorting means is adapted to maintain a short circuit across said first pair of contacts until after the expiration of said first interval and to remove said short circuit a second predetermined interval after said clock starts which second interval is longer than said first interval, and said second shorting means is also adapted to short-circuit between said contact connected to the ungrounded side of said detonator and said contact that is connected to said battery 21 third predetermined interval after said clock starts which third interval is longer than said second interval,

15. In a radio-controlled proximity fuze having a detonator, an electrical circuit having an energizing interval during which a potential is supplied to said circuit, an arming interval during which said detonator is triggered by a signal reflected from a target approached by said fuze and a self-destroying interval during which said detonator is triggered by said circuit, and a portion adapted to be manually rotated to set effective target time and said intervals with respect to a normal position, switching means comprising a clock within said fuze adapted to be started when a projectile containing said fuze is fired, an annular insulating ring engaging said rotatable portion and having on the inner circumference thereof a first pair of electrical contacts providing said energizing interval and adapted when short-circuited to complete said electrical circuit to activate said fuze, a second pair of electrical contacts providing said arming interval and adapted when short circuited to maintain said fuze unarmed, and a third pair of contacts providing said self-destroying interval and adapted when short-circuited to complete an electrical circuit to detonate said fuze, an insulating disk arranged within said annular ring and rotatably driven by said clock with respect to said ring and said normal position and having on the outer circumference thereof first shorting means adapted to short-circuit said first pair of contacts first predetermined interval after said projectile is fired which interval is a function of said effective target time, and second shorting means for maintaining a short circuit across said second pair at the end of said first interval and for removing said short circuit a second predetermined interval after said fuze is fired which second interval is also a function of said effective target time and longer than said first interval, said second shorting means also being adapted to shortcircuit said third pair of contacts a third predetermined interval after said projectile is fired which third interval is also a function of said effective target time and longer than said second interval.

16. In a radio-controlled proximity fuze including a detonator, an electrical circuit having an energizing interval during which a potential is supplied to said circuit and an arming interval during which said detonator is triggered by a signal reflected from a target ap proached by said fuze, and a portion adapted to be manually rotated for setting an effective target time and said intervals with respect to a normal position, circuit actuating means rendered operative upon rotation of said portion and adapted to be moved from said normal position to a position for initiating said energizing interval after an interval in flight which is a function of said effective target time and to a position for initiating said arming interval after an interval in flight which is a function of said effective target time and greater than that for said energizing interval, and centrifugallyoperated means operatively connected to said circuit actuating means and adapted to be rendered operative upon setting of the target time by said portion and upon a predetermined rotational speed of said fuze for moving said actuating means from said normal position to said second-mentioned positions.

17. In a radio-controlled proximity fuze including a detonator, an electrical circuit having an energizing interval during which a potential is supplied to said circuit, an arming interval during which said detonator is triggered by a signal reflected from a target approached by said fuze, and a self-destroying interval during which said detonator is triggered by said circuit, and a portion adapted to be manually rotated for setting an effective target time and said intervals with respect to a normal position, circuit actuating means rendered operative upon rotation of said portion and adapted to be moved from said normal position to a position for initiating said energizing interval after an interval in flight which is a function of said effective target time, to a position for initiating said arming interval after an interval in flight which is a function of said effective target time and greater than that for said energizing interval and to a position for initiating said self-destroying interval after an interval in flight which is a function of said effective target time and greater than that for said arming interval, and centrifugally-operated means operatively connected to said circuit actuating means and adapted to be rendered operative upon setting of the target time by said portion upon a predetermined rotational speed of said fuze for moving said circuit actuating means from said normal position to second-mentioned positions.

18. In a radio-controlled proximity fuze including a detonator, an electrical circuit having an energizing interval during which a potential is supplied to said circuit, a'n arming interval during which said detonator is triggered by a signal reflected from a target approached by said fuze, and a self-destroying interval in which said detonator is triggered by said circuit, and a portion adapted to be manually rotated for setting an effective target time and said intervals with respect to a normal position, centrifugally-operated switch means arranged in said circuit and adapted to be released upon failure to rotate said portion and the application of a set back force to said fuze for initiating said energizing interval, timing means arranged in said circuit to provide a time delay upon release of said switch means and upon failure to rotate said portion for initiating said arming interval only after a predetermined interval in flight, circuit actuating means adapted to be rendered operative upon release of said switch means and moved from said normal position to a position for initiating said selfdestroying interval after a predetermined interval in flight which is greater than said time delay, and a centrifugally-operated means operatively connected to said circuit actuating means and adapted to be rendered operative upona predetermined rotational speed of said fuze for moving said circuit actuating means from said normal position to said second-mentioned position.

19. In a radio-controlled proximity fuze having a detonator, electrical means for exploding said detonator triggered by a signal reflected from a target approached by said fuze, and a portion adapted to be rotated to set effective target time, the combination of switching means for completing electrical circuits for activating said fuze a predetermined interval after a projectile containing said fuze is fired if no time setting is made, switching means for completing electrical circuits for arming said fuze a predetermined interval after said fuze is activated if no time setting is made, and means for completing electrical circuits for exploding said detonator in order to self-destroy said fuze a predetermined interval after said projectile is fired if no time setting is made, said self-destruction interval being longer than said activating and arming intervals. 

1. In a radio-controlled proximity fuze having a portion adapted to be rotated to set effective target time, a clock within said fuze adapted to be started When a projectile containing said fuze is fired, said rotatable portion being provided with at least two pairs of electrical contacts the first of which is adapted when short-circuited to close an electrical circuit to activate said fuze and the second of which is adapted when short-circuited to maintain said fuze unarmed, and means short-circuiting said second pair during a portion of the flight of the projectile and rotatably driven by said clock for sequentially short-circuiting said first pair and maintaining said electrical circuit closed and removing the short circuit across said second pair after predetermined intervals in flight which are functions of said effective target time.
 2. In a radio-controlled proximity fuze having a portion adapted to be rotated to set effective target time, switching means comprising a clock within said fuze adapted to be started when a projectile containing said fuze is fired, said rotatable portion being provided with three pairs of electrical contacts insulated from each other, the first of which is adapted when short-circuited to complete an electrical circuit to activate said fuze, the second of which is adapted when short-circuited to complete an electrical circuit to maintain said fuze unarmed, and the third of which is adapted when short-circuited to complete an electrical circuit to self-destroy said fuze, and means short-circuiting said second pair during a portion of the flight of the projectile and rotatably driven by said clock for sequentially short-circuiting said first pair, removing the short circuit from across said second pair, and short-circuiting said third pair at predetermined intervals after said projectile is fired which intervals are functions of said effective target time setting.
 3. Switching means for a radio-controlled proximity fuze in accordance with claim 2 and including a centrifugally-operated switch adapted when operated to close an electrical circuit to activate said fuze and to prepare an electrical circuit to self-destroy said fuze, a fourth pair of contacts on said rotatable portion adapted when short-circuited to complete said circuit to self-destroy said fuze, and means to prevent said centrifugal switch from operating if a time setting is made, and in which said short-circuiting means is adapted to short-circuit between said fourth pair of contacts a predetermined interval after said projectile is fired if no time setting is made.
 4. Switching means for a radio-controlled proximity fuze in accordance with claim 2 and in which said shorting means is adapted to sequentially short-circuit across said first pair, remove the short circuit from across said second pair and to short-circuit said third pair at predetermined intervals after said projectile is fired if no time setting is made.
 5. In a radio-controlled proximity fuze, a generally tubular body portion having an outwardly extending flange near the front end thereof contoured to form part of the ogive of a projectile, a generally conical nose portion contoured to complete said ogive and having a rearwardly extending cylindrical portion fitting and rotatable within said body portion to set effective target time, means for preventing relative axial movement between said nose and said body portions, said nose portion containing a battery and amplifier and oscillating-detector circuits, an electrical detonator within said body portion, a clock also within said body portion adapted to be started when a projectile containing said fuze is fired, a pair of conducting rings within said body portion insulated from each other and spaced along the axis of said body portion with the rings connected to opposite sides of said detonator, a pair of brushes on said cylindrical portion each of which is resiliently urged against one of said conducting rings and connected to an electrical circuit within said nose portion, said cylindrical portion also being provided with at least one pair of electrical contacts insulated from each other and adapted to switch aN electrical circuit within said nose portion when short-circuited together, and means rotatably driven by said clock and adapted to short-circuit said contacts.
 6. In a fuze in accordance with claim 5 in which said rotatably-driven means short-circuits a pair of electrical contacts during a portion of the interval in flight and is adapted to remove this short circuit when rotated.
 7. In a radio-controlled proximity fuze having an oscillating detector adapted to oscillate at radio frequency and to detect the difference beat frequency between the signal radiated by said fuze and a signal reflected from a target approached by said fuze, an amplifier for amplifying said detected signal, an electrically-actuated detonator adapted to initiate the explosion of said fuze, a grid-controlled gas-filled discharge tube adapted to actuate said detonator when triggered by the output of said amplifier, a battery, and a portion adapted to be rotated to set an effective target time, an energizing interval, an arming interval, and a self-destruction interval; switching apparatus comprising means for normally maintaining a short circuit across said detonator, means for completing an electrical circuit during said self-destruction interval to connect said battery to said detonator in order to self-destroy said fuze after an interval in flight which is a function of said effective target time providing said fuze has not detonated from a signal reflected from a target, means for removing the short circuit across said detonator during said arming interval and a predetermined interval before said fuze self-destroys, and means for completing an electrical circuit during said energizing interval to connect said battery to said amplifier and said detector and said discharge tube a predetermined interval before the removal of said short circuit.
 8. In a radio-controlled proximity fuse in accordance with claim 7 in which said switching apparatus includes a separate switching means operable when no time setting is made for completing an electrical circuit during said energizing interval to connect said battery to said amplifier and said detector and said discharge tube in order to activate said fuze a first predetermined interval after said projectile is fired, for removing said short circuit from across said detonator during said arming interval to arm said fuze a second predetermined interval after said projectile is fired, and for completing an electrical circuit during said self-destruction interval to connect said battery to said detonator a third predetermined interval after said projectile is fired.
 9. In a radio-controlled proximity fuze having an oscillating detector adapted to oscillate at radio frequency and to detect the difference beat frequency between the signal radiated by said fuze and a signal reflected from a target approached by said fuze, an amplifier for amplifying said detected signal, an electrically-actuated detonator adapted to initiate the explosion of said fuze, a grid-controlled gas-filled discharge tube adapted to actuate said detonator when triggered from the output of said amplifier, a battery, and a portion adapted to be rotated to set effective target time; switching apparatus comprising a clock adapted to be started when a projectile containing said fuze is fired, a pair of juxtapositioned coaxial disks of insulation one of which engages said rotatable portion and the other of which is rotatably driven by said clock, a pair of spaced electrical contacts on the face of one disk one of which contacts is electrically connected to said battery, a centrifugally-operated switch having a set of normally open contacts adapted when closed to complete an electrical circuit to connect said battery to said amplifier and to said detector and to said discharge tube in order to activate said fuze and a set of break-make contacts adapted when said switch is operated to open a circuit normally maintaining a short circuit across said detonator to arm said fuze and to electrically cOnnect said detonator to the other of said spaced contacts, means to prevent said centrifugal switch from operating if a time setting is made, and a shorting member on the contiguous face of the other disk adapted to short-circuit between said spaced contacts a predetermined interval after said projectile is fired providing no time setting is made.
 10. Switching apparatus in accordance with claim 9 in which said centrifugal switch is disposed in said rotatable portion and said means to prevent said centrifugal switch from operating includes a pin in the path of movement of said switch and removable therefrom by the force of setback from the firing of said projectile to release said switch, said pin projecting through an aperture in the disk engaging said rotatable portion, said disk driven by said clock having an opening therein in alignment with said pin through which said pin may pass to release said switch if no time setting is made, whereby when a time setting is made said pin is rotated out of alignment with said opening and operation of said centrifugal switch is prevented.
 11. In a radio-controlled proximity fuze having an oscillating detector adapted to oscillate at radio frequency and to detect the difference beat frequency between the signal radiated by said fuze and a signal reflected from a target approached by said fuze, an amplifier for amplifying the output of said detector, an electrically-actuated detonator adapted to initiate the explosion of said fuze and having one side thereof connected to electrical ground, a grid-controlled gas-filled discharge tube adapted to actuate said detonator when triggered by a signal of sufficient amplitude and duration from said amplifier, a battery, and a portion adapted to be rotated to set effective target time; switching apparatus comprising a clock within said fuze adapted to start when a projectile containing said fuze is fired, a pair of juxtapositioned coaxial disks of insulation the first of which engages said rotatable portion and the second of which is rotatably driven by said clock, said first disk having a plurality of concentric arcuate electrical contacts on the face thereof including an inner ring contact normally electrically connected to the ungrounded side of said detonator, an arcuate second contact spaced radially from said inner contact and connected to electrical ground, an arcuate third contact having the same radius as said second contact and electrically connected to said battery and being disposed centrally of the open portion of said second contact, the circumferential separation between the second and third contacts subtending a central angle phi , and a pair of arcuate radially-spaced outer contacts of greater radius than said second and third contacts and subtending a central angle including and greater than the angle phi , one of said outer pair being electrically connected to said battery and the other of said pair being electrically connected to the anode circuits of said detector and said amplifier and said discharge tube, said second disk having a pair of radially aligned shorting members on the contiguous face thereof the first of which is adapted to short-circuit between said ring and said second contacts when a time setting is made and to remove this short circuit after an interval in flight which is a function of said effective time setting and the second of which is adapted to short circuit between said pair of outer contacts a predetermined interval before said first shorting member removes the short across said ring and said second contacts as said second disk is rotated by said clock, said first shorting member being also adapted to short-circuit between said ring and third contacts after rotation through said angle phi .
 12. In a radio-controlled proximity fuze having an oscillating detector adapted to oscillate at radio frequency and to detect the difference frequency between the radiated signal and a signal reflected from a target approached by said fuze, an amplifier for amPlifying the output of said detector, an electrically-actuated detonator adapted to initiate the explosion of said fuze and having one side thereof connected to electrical ground, a grid controlled gas-filled discharge tube adapted to actuate said detonator when triggered by a signal of sufficient amplitude and duration from said amplifier, a battery, and a portion adapted to be rotated to set effective target time; switching apparatus comprising a clock within said fuze adapted to start when a projectile containing said fuze is fired, a first pair of electrical contacts on said rotatable portion one of which is connected to electrical ground and the other of which is electrically connected to the ungrounded side of said detonator, a second pair of electrical contacts on said rotatable portion one of which is electrically connected to said battery and the other of which is connected to the plate circuits of said amplifier and said detector and said discharge tube, a contact member on said rotatable portion also electrically connected to said battery, means rotatably driven by said clock for short-circuiting said first pair of contacts when an effective target time setting is made, and adapted to remove the short circuit a first predetermined interval after said clock starts which interval is a function of said effective target time setting, means rotatably driven by said clock for short-circuiting said second pair of contacts a second predetermined interval after said clock starts, said second interval being shorter than said first interval and also being a function of said time setting, and means rotatably driven by said clock for short-circuiting the contact of said first pair which is connected to said detonator and said contact member a third predetermined interval after said clock starts which third interval is also a function of said effective target time setting and greater than said first interval.
 13. In a radio-controlled proximity fuze having a portion adapted to be rotated to set effective target time, an electrically-actuated detonator having one side thereof grounded and adapted to initiate the explosion of said fuze, an oscillating detector within said rotatable portion adapted to oscillate at radio frequency and to detect the beat frequency between the signal radiated by said fuze and a signal reflected from a target approached by said fuze, an amplifier within said rotatable portion for amplifying said detected signal, a grid-controlled gas-filled discharge tube within said rotatable portion adapted to actuate said detonator when triggered by the output of said amplifier, and a battery within said rotatable portion; switching means comprising a clock within said fuze adapted to be started when a projectile containing said fuze is fired, an annular insulating ring engaging said rotatable portion and provided with a first pair of spaced electrical contacts on the inner circumference thereof with each contact connected to an opposite side of said detonator and a second pair of spaced electrical contacts on the inner circumference thereof one of which is connected to said battery and the other of which is connected to the anodes of said detector and said discharge tube and said amplifier, an insulating disk within said annular ring rotatably driven by said clock and provided with first shorting means adapted to short-circuit said second pair of contacts a first predetermined interval after said clock starts which interval is a function of said effective target time, and second shorting means adapted to short-circuit said first pair of contacts during the shorting of said second pair and to remove the short circuit across said first pair a second predetermined interval after said clock starts which second interval is a function of said effective target time and longer than said first interval, said second shorting means also being adapted to short-circuit said contact of said first pair that is connected to the ungrounded side of said detonator and the contact of saiD second pair that is connected to said battery a third predetermined interval after said clock starts which interval is a function of said effective target time and greater than said second interval.
 14. Switching means in a radio-controlled proximity fuze in accordance with claim 13 and in which, when no effective target time setting is made, said first shorting means is adapted to short-circuit said second pair of contacts a first predetermined interval after said clock starts and said second shorting means is adapted to maintain a short circuit across said first pair of contacts until after the expiration of said first interval and to remove said short circuit a second predetermined interval after said clock starts which second interval is longer than said first interval, and said second shorting means is also adapted to short-circuit between said contact connected to the ungrounded side of said detonator and said contact that is connected to said battery a third predetermined interval after said clock starts which third interval is longer than said second interval.
 15. In a radio-controlled proximity fuze having a detonator, an electrical circuit having an energizing interval during which a potential is supplied to said circuit, an arming interval during which said detonator is triggered by a signal reflected from a target approached by said fuze and a self-destroying interval during which said detonator is triggered by said circuit, and a portion adapted to be manually rotated to set effective target time and said intervals with respect to a normal position, switching means comprising a clock within said fuze adapted to be started when a projectile containing said fuze is fired, an annular insulating ring engaging said rotatable portion and having on the inner circumference thereof a first pair of electrical contacts providing said energizing interval and adapted when short-circuited to complete said electrical circuit to activate said fuze, a second pair of electrical contacts providing said arming interval and adapted when short circuited to maintain said fuze unarmed, and a third pair of contacts providing said self-destroying interval and adapted when short-circuited to complete an electrical circuit to detonate said fuze, an insulating disk arranged within said annular ring and rotatably driven by said clock with respect to said ring and said normal position and having on the outer circumference thereof first shorting means adapted to short-circuit said first pair of contacts first predetermined interval after said projectile is fired which interval is a function of said effective target time, and second shorting means for maintaining a short circuit across said second pair at the end of said first interval and for removing said short circuit a second predetermined interval after said fuze is fired which second interval is also a function of said effective target time and longer than said first interval, said second shorting means also being adapted to short-circuit said third pair of contacts a third predetermined interval after said projectile is fired which third interval is also a function of said effective target time and longer than said second interval.
 16. In a radio-controlled proximity fuze including a detonator, an electrical circuit having an energizing interval during which a potential is supplied to said circuit and an arming interval during which said detonator is triggered by a signal reflected from a target approached by said fuze, and a portion adapted to be manually rotated for setting an effective target time and said intervals with respect to a normal position, circuit actuating means rendered operative upon rotation of said portion and adapted to be moved from said normal position to a position for initiating said energizing interval after an interval in flight which is a function of said effective target time and to a position for initiating said arming interval after an interval in flight which is a function of said effective target time And greater than that for said energizing interval, and centrifugally-operated means operatively connected to said circuit actuating means and adapted to be rendered operative upon setting of the target time by said portion and upon a predetermined rotational speed of said fuze for moving said actuating means from said normal position to said second-mentioned positions.
 17. In a radio-controlled proximity fuze including a detonator, an electrical circuit having an energizing interval during which a potential is supplied to said circuit, an arming interval during which said detonator is triggered by a signal reflected from a target approached by said fuze, and a self-destroying interval during which said detonator is triggered by said circuit, and a portion adapted to be manually rotated for setting an effective target time and said intervals with respect to a normal position, circuit actuating means rendered operative upon rotation of said portion and adapted to be moved from said normal position to a position for initiating said energizing interval after an interval in flight which is a function of said effective target time, to a position for initiating said arming interval after an interval in flight which is a function of said effective target time and greater than that for said energizing interval and to a position for initiating said self-destroying interval after an interval in flight which is a function of said effective target time and greater than that for said arming interval, and centrifugally-operated means operatively connected to said circuit actuating means and adapted to be rendered operative upon setting of the target time by said portion upon a predetermined rotational speed of said fuze for moving said circuit actuating means from said normal position to second-mentioned positions.
 18. In a radio-controlled proximity fuze including a detonator, an electrical circuit having an energizing interval during which a potential is supplied to said circuit, an arming interval during which said detonator is triggered by a signal reflected from a target approached by said fuze, and a self-destroying interval in which said detonator is triggered by said circuit, and a portion adapted to be manually rotated for setting an effective target time and said intervals with respect to a normal position, centrifugally-operated switch means arranged in said circuit and adapted to be released upon failure to rotate said portion and the application of a set back force to said fuze for initiating said energizing interval, timing means arranged in said circuit to provide a time delay upon release of said switch means and upon failure to rotate said portion for initiating said arming interval only after a predetermined interval in flight, circuit actuating means adapted to be rendered operative upon release of said switch means and moved from said normal position to a position for initiating said self-destroying interval after a predetermined interval in flight which is greater than said time delay, and a centrifugally-operated means operatively connected to said circuit actuating means and adapted to be rendered operative upon a predetermined rotational speed of said fuze for moving said circuit actuating means from said normal position to said second-mentioned position.
 19. In a radio-controlled proximity fuze having a detonator, electrical means for exploding said detonator triggered by a signal reflected from a target approached by said fuze, and a portion adapted to be rotated to set effective target time, the combination of switching means for completing electrical circuits for activating said fuze a predetermined interval after a projectile containing said fuze is fired if no time setting is made, switching means for completing electrical circuits for arming said fuze a predetermined interval after said fuze is activated if no time setting is made, and means for completing electrical circuits for exploding said detonator in order to self-destroy said fuze a predetermined iNterval after said projectile is fired if no time setting is made, said self-destruction interval being longer than said activating and arming intervals. 